This type of compensation device is the TSC subclass in SVC classification. Due to the susceptibility of thyristors to damage from surge currents, they must be triggered by zero crossing, which means that a triggering signal is emitted at the moment when the voltage across the thyristor is zero. Zero crossing triggering technology can achieve no inrush current input into capacitors. In addition, due to the unlimited triggering times of thyristors, it can achieve quasi dynamic compensation (response time in milliseconds), making it suitable for frequent switching of capacitors and very suitable for frequently changing load conditions. The conduction voltage drop of the thyristor is about 1V, and the loss is significant (taking a compensation device with a rated capacity of 100Kvar as an example, if the rated current of each phase is about 145A, the rated conduction loss of the thyristor is 145 × 1 × 3=435W), requiring the use of large-area heat sinks and ventilation fans. Thyristors are highly sensitive to voltage change rate (dv/dt) and can easily be misled and damaged by surge currents in the event of voltage transients such as overvoltage and lightning strikes. Even if lightning arresters are installed, it is of no use because they can only limit the peak voltage and cannot reduce the voltage change rate.
This type of compensation device has a complex structure, high price, poor reliability, and high losses. Except for situations where the load changes frequently, it has almost no practical value in other situations.